Geologic Structure of Kozjansko Between Savinja River and Rudnica Mountain Part One: Younger Paleozoic and Mesozoic
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RMZ - Materials and Geoenvironment, Vol 50, No 3, pp 663-685, 2003 665 Geologic Structure of Kozjansko between Savinja River and Rudnica Mountain Part one: Younger Paleozoic and Mesozoic Geoloka zgradba Kozjanskega med Savinjo in Rudnico Prvi del: mlaji paleozoik in mezozoik STEVO DOZET Geoloki zavod Slovenije, Dimièeva 14, 1001 Ljubljana, Slovenija, E mail: stevodozet@geo-zssi Received: October 15, 2003 Accepted:December 10, 2003 Abstract: The geological structure of the area between the Savinja River and Loka at usem, comprising the Tertiary complex and its Pre-Tertiary basement, has been described in this paper" Geologically, this area belongs to the Sava Folds, and with regard to geogra- phy to the western and central part of Kozjansko" The area between the Savinja River and Loka at usem is built of the Younger Paleozoic, Mesozoic, Tertiary and Quater- nary rocks" The most extended are the synclinally folded Tertiary beds, whereas the Paleozoic and Mesozoic rocks crop out along the edge of the Tertiary synclines" Among the Paleozoic rocks only the Younger Paleozoic ones have been ascertained at the sur- face" The Triassic system is more or less completely developed, while the Cretaceous and Jurassic rocks are preserved only in part and locally" The Tertiary system consists of the Pseudo-Socka, Egerian, Badenian and Sarmatian beds" The geological and geophysical investigations showed an extremely strong tectonic displacement of the whole area" Such structure is a consequence of folding and later cutting of the area with numerous faults in various directions" Tectonics reached generally as the Tertiary as the Quater- nary beds and the Pre-Tertiary basement" The rocks were subjected to several types of deformations" The strongest folding was in Ottnangian and Karpatian" Strong deforma- tions of the Tertiary beds also originated after the deposition of the Sarmatian beds during the Attic orogenetic phase, which was active in the Lower Pliocene" The main folding was caused by forces taking an active part in direction from north to south" Izvleèek: V tem èlanku opisujemo geoloko zgradbo ozemlja med reko Savinjo in Loko pri usmu, ki obsega terciarni kompleks in njegovo predterciarno podlago" Geoloko pripada to ozemlje Posavskim gubam, geografsko pa zahodnemu in osrednjemu delu Kozjanskega" Ozemlje med Savinjo in Loko pri usmu je zgrajeno iz mlajepaleozojskih, mezozojskih, terciarnih in kvartarnih kamnin" Najbolj razirjene so sinklinalno nagubane terciarne plasti, paleozojske in mezozojske kamnine pa izdanjajo v jedrih antiklinal in na obrobju terciarnih sinklinal" Med paleozojskimi kamninami so na povrini ugotovljene le mlajepaleozojske" Triasni sistem je bolj ali manj popolno razvit, kredne in jurske kamnine pa so ohranjene le delno in lokalno" Terciarni sistem sestavljajo psevdosoteke, egerijske, badenijske in sarmatijske plasti" Geoloke in geofizikalne raziskave so pokazale izredno moèno tektonsko dislociranost celotnega ozemlja" Taka zgradba je posledica gubanja in naknadnega razkosanja ozemlja z mnoico prelomov razliènih smeri" Tektonika Scientific paper 666 DOZET, S je zajela v splonem tako terciarne kot kvartarne plasti in predterciarno podlago" Kamnine so bile podvrene veè vrstam deformacij" Najveèje gubanje je bilo v ottnangiju in karpatiju" Moène deformacije terciarnih plasti so nastale tudi po odloitvi sarmatijskih plasti v èasu attike orogenetske faze, ki je delovala v spodnjem pliocenu" Glavno gubanje so povzroèili pritiski, ki so delovali v smeri od severa proti jugu" Key words: Stratigraphy, tectonics, environment, paleogeography, Sava Folds, Eastern Slovenia" Kljuène besede: stratigrafija, tektonika, okolje, paleogeografija, Posavske gube, vzhodna Slovenija" INTRODUCTION REVIEW OF PREVIOUS INVESTIGATIONS The Kozjansko area between the Savinja The ZOLLIKOFERS (1861/62) description of River and the Rudnica Mountain was the Tertiary beds among the Konjika Gora, mapped in detail on the scale of 1:10 000 in Macelj, the Sotla and the Savinja River was the frame of the investigation programme for one of the first and most important geologi- the underground gas storage! According to cal publications! This work was the basis for the Petrol Ljubljana order several localities the BITTNERS (1884) and other subdivisions in Slovenia were proposed by the Geologi- of the Tertiary in this area! STUR (1871a, b) cal Survey of Ljubljana! In accordance with described the Neogene beds of the wider afore mentioned Petrol Ljubljana, DO area! He noticed that the Socka Beds of Zemeljski Plin and Geological Survey Lako originated in the fresh water Ljubljana made a contract to do a geological enviroment and that toward the east a brack- and geophysical prospection among other of ish and marine fauna prevails! Bittner divided two following localities: marjeta-Lahomno the Tertiary beds between Lako and Zagorje and the Rudnica Anticline! A detailed geo- into the: 1!) Socka Beds with coal, 2!) the logical mapping of the marjeta-Lahomno marine Miocene beds (Marine Clay and area was carried out in the year 1983! As the Green Sandstone, the Lower Leitha basis of our mapping served the Geological Limenstone, the Lako Marl and the Upper Map of Slovenia S 1:100 000 (BUSER, 1978), Leitha Limestone) as well as 3!) the brack- made by Geological Survey of Ljubljana! ish Sarmatian beds! TELLER (1889) brought With the scope of underground gas storage into the geological terminology the name construction fundamental geologic, Pseudo-Zilian Beds! With this name he des- geoelectric and magnetometric investiga- ignated the shales and claystones from the tions for reconnaissance of underground geo- Celje castle, for which the previous research- logic structure of the area between entjur, ers beleived, they were of the Carboniferous Planina, Trobni Dol and Loka at usem were age! PETRASCHECK (1926/29) assigned the performed in the years 1985 and 1986! Socka Beds to Chattian! Within the Ter- tiary beds he distinguished two coal horizons: (1) older, from the limnic and brackish Socka Beds and (2) younger, from the Aquitanian marine beds! He quoted two dis- RMZ-M&G 2003, 50 Geologic Structure of Kozjansko between Savinja River and Rudnica Mountain 667 cordances within the Tertiary succession! the tectonic structure of the Tertiary belt in MUNDA (1939, 1942, 1953) correlated the the Lako Syncline, composed of several Socka Beds of Senovo, Trobni Dol, parallel synclines and separated by anticlines Zagorje, Medvode and Bohinj! Taking into and dislocations, he used the name account their fossil contents, he came to the synclinorium PLENIÈAR (1971) wrote the conclusion, that the coal formation cannot explanatory text of the Celje Map Sheet be of Miocene age! HAMRLA (1954, 1955) 1:100 000 describing the geological struc- described in detail the Pre-Tertiary basement ture of this area PREMRU (1975) exposed the as well as Oligocene and Miocene beds along nappe structure of the central part of the Sava the northern border of the Lako Syncline Folds He gave another informations prov- east of the Savinja River! In the second ar- ing the nappe structure of the Sava Folds ticle, he described the geology of the Rudnica KUÈER (1975) did not agree with the area with regard to the occurrence of some Premrus nappe interpretation of this area, ores! NOSAN (1956) distinguished three fa- disagreeing especially with the existence of cial types of the Socka Beds: a) the larger nappe structures BABIÆ (1979) exam- Socka Beds at Zagorje-Hrastnik-Trbovlje, ined the limestones with calpionellids in sev- b) the Socka Beds in the Senovo Basin and eral small outcrops on the Rudnica Moun- c) the Socka Beds between Pohorje and tain The Calpionella alpina and Calpionella Bohor! PLENIÈAR AND NOSAN (1958) pre- elliptica subzones and the Calpionellopsis sented the paleogeography of the Pannonian zone have been recognized corresponding to borderland in Slovenia According to the the Uppermost Tithonian and Berriasian authors the Pannnonian Sea transgressed the central part of Slovenia during the Upper Most of field and laboratorial data have been Oligocene RIJAVEC (1958, 1959, 1965, 1966, obtained so far at systematic geological in- 1970, 1971, 1974, 1976 a, b, 1983) deter- vestigations in the frame of the Basic Geo- mined the Tertiary microfauna between the logical Map of SFRY S 1:100 000 on the Map Rudnica and Boè Mt, Loka at usem, Sheet Celje In the manuscript and printed marje at Jele, in the Trobni Dol area as materials of the Map Sheet Celje various well as between Lako and Grahove NOSAN lithological developments, lithostratigraphic (1960) reported on the geological mapping units and members, fossil findings, traces of of the area between the Konjika Gora and volcanic activity, mineral deposits and the Sava River He emphasized that the fold- tectonical structures of the area have been ing affected the Tertiary sediments as well represented and described in detail Hower, as the Tertiary basement GRAD (1961, 1967) the data of the systematic regional mapping described geological conditions between the and investigations contributed most informa- Rudnica Mountain and the Sava River as well tions to the knowledge of the geological as the geology of the Kozjansko area He structure of Kozjansko and wider considered that the main folding in the area neighbourhood The results of this mapping was Post-Pannonian KUÈER (1962, 1967) are presented in the explanatory text written wrote a dissertation about Zagorje Tertiary by BUSER (1978, 1979 a) The above-men- He attributed the main folding to the